Use self-join to delete duplicate rows

The most effective way to detect duplicate rows is to join the table against itself as shown below.

select
   book_unique_id,
   page_seq_nbr,
   image_key
from
   page_image a
where
   rowid >
     (select min(rowid) from page_image b
      where
         b.key1 = a.key1
      and
         b.key2 = a.key2
      and
         b.key3 = a.key3
      );